Mich. Comp. Laws § 41.278
On the making of the said final order, the commissioners shall proceed to let the contract for the construction of the proposed improvement to the lowest responsible bidder, said bidder to furnish adequate security for the performance of the same, in a sum to be fixed by the commissioners: Provided, That no contract shall be let or rolls spread under the provisions of this act when 25 per cent or more of the total tax levied for all purposes upon real property within the assessment district shall have been delinquent for 1 or more years. The commissioners shall give notice of the letting of such contract by publishing a notice thereof in some newspaper of general circulation in the county, at least once in each week for 2 weeks, and may publish notice thereof in other newspapers if they shall deem the same advisable. At least 1 publication of the notice shall be made not less than 10 days prior to the date of letting. They may reserve the right to reject any and all bids. If rejected, the same procedure for obtaining bids shall be repeated, or if deemed advisable by the commissioners, they shall proceed with the construction of said proposed improvement in the same manner and with the same authority, when applicable, as they have to build roads under the provisions of the county road law. After the bids have been received or as soon thereafter as practicable, the commissioners shall enter into the necessary contract for the construction of the proposed improvement with the party whose bid shall be accepted by them and who shall have furnished the bonds required. The commissioners shall take such action as may be necessary to commence construction of the proposed improvements, or cause such construction to be commenced, within 6 months, or if weather does not then permit, as soon thereafter as the weather does permit after making said final order.
MCL 41.278